Embodiments of the invention relate generally to data storage systems, and more particularly to a method and apparatus for retrieving data from a data storage system.
Data have become one of most important resources for an enterprise. The data universe is forecast to reach 35.2 ZBytes in 2020 (1 ZByte=1 million PetaBytes), 44 times the estimated storage size in 2009. The data amount grows almost exponentially, which causes an enterprise to constantly purchase a considerable number of storage devices to satisfy the increasing demand for storage. However, studies show that the utilization efficiency of storage in an enterprise is often less than 50%, so the investment return rate of storage is at a quite low level.
In order to satisfy the soaring demand for data storage, solutions have been proposed to reduce the space occupied by data, simplify the storage management, and utilize existing resources to the utmost so as to reduce costs. These solutions may involve storage resource consolidation, dynamic configuration in storage capacity, curtailing storage capacities, information life cycle management, and reducing energy consumption.
One important technique for managing data storage is thin provisioning. A core principle of thin provisioning is to present to an operating system that it has access to a storage system with a very large storage space, while the actual physical storage space is not so large. A storage system that uses thin provisioning technique does not allocate too much space to an application all at once. Instead, it will allocate less space to the application in multiple times based on the volume actually required by this application. When the allocated volume space is not enough with the increase of the data generated by this application, the system will supplement some storage space from a backend storage pool.
However, it takes longer time to retrieve data from a storage system that uses thin provisioning; thus impacting the performance of the system. It is therefore desirable to reduce the data retrieving time for a storage system that uses a thin provisioning technology.